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Tig Welding Aluminum Norms

I am a self taught welder. I have tig welded for over 10 years, mainly steel stainless and silicon bronze. I would consider myself a very good welder. I have recently started working a lot with aluminum and am getting frustrated with what I feel are non satisfactory welds (mainly the presents of porosity).

The thing is that since I am self taught I don't know exactly what you should be able to achieve.

I weld mainly 1/4" 6061/6063 with 4043 filler rod. I have a brand new Dynasty 350.

An example of difficulty I am having is the following:

I am making a frame out of 2.5" 6063 square tubing with .25" wall. I miter the tube and bevel the ends to receive weld so I can grind flush. I use walter grinding discs made for aluminum. After I grind I sand off any burrs, clean with lacquer thinner and then wire brush with dedicated stainless brush. I clamp the frame down to my table and begin to weld. When I first puddle the joint and add a bit of filler rod, if I continue to hold the arc over the puddle it just bubbles. In fact any time I strike an arc and form a weld puddle on Aluminum it will just sit there and bubble. Is this normal? I don't see how it is possible to get a porosity free weld if my puddle is bubbling. I am running straight argon at about 20-25. I am welding at about 250 amps with 1/8" zirconiated tungsten with a gas lens. I have messed with all the setting to no avail.

The other 'is this normal' question I have is: with the afore mentioned settings, how long should my tungsten tip last? I grind them to a truncated point with the flat spot being at least 1/16" in diameter and I only get about 6" of weld before the tip start to deform (starts melting and splitting at tip).

Lose the zirconated tungsten. For AC welding on an inverter, I prefer the 2% Lanthanated. Second choice would be ceriated. The zirconated tungsten performs best on the squarewave machines, in lieu of the pure (green).

Try using 5356 filler vs the 4043. Think you'll have better results. I'd be using 1/8" filler for that job.

Gas flow is fine. Since you haven't experienced problems welding SS, I'm going to assume that there's no problem with covering gas.

As mentioned, a #8 cup will be your best choice here.

As mentioned, acetone vs thinner works better.

Set your balance to about 85%. On new, clean material, that's all the cleaning you'll need.

Aluminum is different than steel. As soon as you get your puddle, add filler and move. By staying in one place you're "cooking" the material. Aluminum likes to be welded hot and fast. Welding hot and fast also reduces the size of the HAZ.

Don't futz with the pulser or the independent amplitude adjustments. The Dynasty will weld that joint just fine without them.

It will take a little time to adjust to aluminum (vs SS and mild steel), but I think the biggest problem you're having is staying in one place too long and cooking (overheating/boiling) your base metal.

Once you get started, and the material starts to build heat, you'll find you need to back off on the amps or your puddle will get too fluid (wide).

I prefer a dry band saw for cutting aluminum, The cut off wheels and sanding discs do nothing but contaminate.

I use 1.5% Lanthanated which is what My Dynasty 300 came with and have never had a problem.

Dont let the tungsten stick out much more than 1/8 to 3/16" past the cup.

If you use a small cup with high gas flow you can have a ventury affect that will pull the outside air in that will also contaminate your weld, So make sure you have a big enouph cup and not to much or to little argon.